Dear Yves,
just upgrated a Joomla Site from Version 2.5.28 to V3.4.8 including all components.
One was Matukio.
I upgrated Matukio from a Version V2 of Matukio to V5.1.3. I did this before I upgrated Joomla and because V5.1.3 still supports Joomla V2.5.x.
Worked great. (I didn't checked the dashboard at that stage)
After Joomla was upgrated to Version 3.4.8 I also updated matukio to the latest version (V5.2.8).
Everything seems fine too.
Everything works fine except the Dashbord looks currupted.
I had a similar effect in the past with hotspots.
Daniel told me there was an old file that needed to be deleted.
May something like that happend here?
Would you like to have a look into the installation?
I can provide you with an account. Please let me know.
The problem is NOT urgent.
Best regards
Bernd